226 MR. C. TATE REGAN ON THE 
2. ANCISTRUS UNDECIMALIS. 
Chetostomus undecimalis Steind. Denkschr. Ak. Wien, xxxix. 1878, p. 43, pl. viii., and xlii. 1880, 
p- 67. 
Plerygoplichthys undecimalis Eigenm. & Eigenm. Proce. Cal. Ac. (2) ii. 1889, p. 44. 
Depth of body 4 times in the total length, length of head 3} times. Head 1} times 
as long as broad and 1$ times as long as deep. Diameter of eye 74 times in the 
length of head, interorbital width 25 times, length of snout twice. Length of mandi- 
bular ramus about 4 times in the interorbital width. Snout narrowed anteriorly ; 
supraoccipital with median ridge ; supraorbital edges not or scarcely raised ; temporal 
plates carinate ; interoperculum armed with 6-8 slender spines, the longest equal to 
1 the length of head. Scutes spinulose, carinate except on the caudal peduncle, 
23-29 in a longitudinal series, 8-9 between dorsal and adipose fin, 12-13 between 
anal and caudal. Supraoccipital entirely bordered posteriorly by a single scute; two 
series of scutes between the nuchal and posthumeral series. Lower surface of head 
and abdomen completely covered with small granular scales, D. I 10, the first ray 
equal to § the length of head, the last as long; length of base of dorsal equal to its 
distance from the caudal. A. I 3-4. Pectoral spine extending nearly to middle of 
ventral. Caudal emarginate, the shortest ray $ the length of the longest, which is 
1! times as long as the head. Caudal peduncle 3 times as long as deep. Greyish, 
with dark spots on head, body, and fins, those on the head smallest, those on the fins 
in a single series between each pair of rays. 
Total length 250 mm. 
One specimen: R. Magdalena. 
3. ANCISTRUS ETENTACULATUS. 
Hypostoma etentaculatum Spix, Gen. Spee. Pisc. p. 7, pl. iv. figs. 1 & 2 (1829). 
Hypostomus duodecimalis Cuy. & Val. Hist. Nat. Poiss. xv. p. 498, pl. cceceliv. (1840). 
Ancistrus longimanus Kner, Denkschr. Ak. Wien, vii. 1854, p. 283. 
Pterygoplichthys duodecimalis Giinth. Cat. Fish. v. p. 251 (1864). 
Pterygoplichthys etentaculatum Eigenm. & Eigenm. Proc. Cal. Ac. (2) ii. 1889, p. 44, and Occ. 
Pap. Cal. Ac. i. 1890, p. 428. 
Depth of body 4} times in the total length, length of head 3 times. Head 14 times 
as long as broad and 14 times as long as deep. Diameter of eye nearly 8 times in the 
length of head, interorbital width 2} times, length of snout 1§ times. Length of 
mandibular ramus 3% times in the interorbital width. Snout narrowed anteriorly ; 
supraoccipital with median ridge ; supraorbital edges slightly raised ; temporal plates 
carinate ; interoperculum armed with 10-12 slender spines, the longest equal to + the 
length of head. Scutes spinulose, carinate except on the caudal peduncle, 28 in a 
longitudinal series, 6 between dorsal and adipose fin, 12 between anal and caudal. 
Supraoccipital entirely bordered posteriorly by a single scute; two series of scutes 
